1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and a method of fabricating an LCD device, and more particularly, to a transmissive-type LCD device and method of fabricating a transmissive-type LCD device.
2. Discussion of the Related Art
As demand for various display devices increases, efforts have been made to develop liquid crystal display (LCD) devices, plasma display panel (PDP) devices, electroluminescent display (ELD) devices, and vacuum fluorescent display (VFD) devices. Among these various flat display devices, the LCD devices have been commonly used as substitutes for cathode ray tube (CRT) devices due to their thin profiles, light weight, and low power consumption. In addition to mobile-type LCD devices, such as displays for notebook computers, the LCD devices have been developed for use in computer monitors and televisions to receive and display broadcasting signals.
Despite various technical developments within the LCD device technology, improved image quality of the LCD devices has been lacking. Accordingly, in order to use the LCD devices as general displays, providing images having high resolution and high luminance with a large-sized screen must be attained while still maintaining their thin profile, light weight, and low power consumption.
In general, a LCD device includes an LCD panel for displaying images and a driving part for supplying driving signals to the LCD panel. In addition, the LCD panel includes first and second glass substrates bonded to each other at a predetermined interval with a liquid crystal layer injected between the first and second glass substrates. The first glass substrate (i.e., TFT array substrate) includes a plurality of gate and data lines, a plurality of pixel electrodes, and a plurality of thin film transistors. The plurality of gate lines are formed along a first direction at fixed intervals, and the plurality of data lines are formed along a second direction perpendicular to the gate lines at fixed intervals, thereby defining a plurality of pixel regions. Accordingly, the plurality of pixel electrodes are formed within the pixel regions in a matrix configuration, and the plurality of thin film transistors are switched according to signals provided to the gate lines so as to supply signals of the data lines to the respective pixel electrodes.
The second glass substrate (i.e., color filter substrate) includes a black matrix layer for shielding portions of the first glass substrate, except for the pixel regions, from light. In addition, a red (R), green (G), and blue (B) color filter layer is provided for displaying various light colors, and a common electrode is used for producing an image.
The LCD device is driven according to optical anisotropy and polarizing characteristics of liquid crystal material. The liquid crystal material includes liquid crystal molecules, wherein each liquid crystal molecule has a long and thin structure to control an alignment direction of the liquid crystal molecules by inducing an electric field to the liquid crystal material. By controlling the alignment direction of the liquid crystal molecules, light passing through the liquid crystal material is refracted according to the alignment direction of the liquid crystal molecules by the optical anisotropy of the liquid crystal material, thereby displaying images.
Currently, active matrix LCD (AM-LCD) devices have been developed because of their high image resolution and ability to display moving images. The AM-LCD devices include a thin film transistor and a pixel electrode connected to the thin film transistor are arranged in a matrix configuration.
The LCD devices are commonly classified into transmissive-type LCD devices that display images by using an additional light source, such as a backlight, and reflective-type LCD devices that make use of ambient light. In the transmissive-type LCD devices, the backlight is provided below the LCD panel to control brightness of the LCD panel according to luminance of the backlight. Thus, the transmissive-type LCD devices are commonly used as monitor displays.
Hereinafter, a related art transmissive type LCD device will be described with reference to the accompanying drawings.
FIG. 1 is a plan view of a transmissive-type liquid crystal display (LCD) device according to the related art, and FIG. 2 is a cross sectional view along I–I′ of FIG. 1 according to the related art. In FIGS. 1 and 2, a transmissive-type LCD device includes a lower substrate 10 having a TFT array, an upper substrate 20 having a color filter array, and a liquid crystal layer 25 between the lower and upper substrates 10 and 20.
As shown in FIG. 1, the lower substrate 10 includes a gate line 11, a data line 12, and a pixel electrode 13, wherein a gate electrode 11a protrudes from a predetermined portion of the gate line 11. In addition, the data line 12, which forms source/drain electrodes 12a and 12b, is formed in perpendicular to the gate line 11, whereby a pixel region is defined by a crossing of the gate and data lines 11 and 12 and the pixel electrode 13 is formed within the pixel region. Then, a semiconductor layer 14, which includes a channel region, is formed above the gate electrode 11a, and the source/drain electrodes 12a and 12b are disposed at both sides of the channel region in the semiconductor layer 14.
As shown in FIG. 2, a gate insulating layer 15 is formed along an entire surface of the lower substrate 10 including the gate electrode 11a and the gate line 11, whereby the semiconductor layer 14 is electrically insulated from the gate electrode 11a. In addition, a passivation layer 16 is formed along an entire surface of the lower substrate 10 including the source/drain electrodes 12a and 12b and the data line 12. Then, a contact hole is formed for exposing a portion of the drain electrode 12b so that the pixel electrode 13 is electrically connected with the drain electrode 12b. The gate insulating layer 15 and the passivation layer 16 may be formed of an inorganic insulating material, such as SiOx or SiNx, or an organic insulating material having a low dielectric constant, such as polyamide compound.
The upper substrate 20 includes a black matrix layer 21 for shielding portions of the lower substrate 10, except for the pixel regions, from the light, a color filter layer 22 for displaying various colors corresponding to the respective pixel regions, and a common electrode 23 formed along an entire surface of the upper substrate 20 including the color filter layer 22.
In general, the transmissive-type LCD device uses the backlight as an inner light source, and the color filter layer 22 is formed of an absorbent-type pigment or dye. Thus, if the backlight emits light at an intensity of 100%, light having a specific wavelength is transmitted through respective red (R), green (G), and blue (B) portions of the color filter layer 22 at an intensity of 33%.
Accordingly, the transmissive-type LCD device according to the related art has the following disadvantages. First, during operation of the transmissive-type LCD device, the backlight requires high voltage to optimize the efficiency of the light emitted from the backlight. However, since the transmissive-type LCD device uses the absorbent-type color filter, the light emitted from the backlight is transmitted at an intensity of 33%. Thus, it is difficult to improve the light efficiency in the transmissive-type LCD device using the absorbing type color filter.